A digital-analog converter (DAC) is a device to change a digital signal into an analog signal. The DAC has been used in a wireless communication system, a voice and image signal processing device, and measurement equipment.
In addition, the DAC can control a motor by converting a digital signal into an analog signal. For example, the DAC may be used for a driver to drive a voice coil motor (VCM) constituting a camera module of a portable terminal.
The VCM of the camera module reciprocates within a relatively short distance. The reciprocation of the VCM changes the position of a lens, thereby providing an automatic focusing (AF) function for an object.
In order to drive the VCM used for the implementation of such an AF function, three factors of linearity, hysteresis, and sensitivity are important. Among this, the linearity is the most important factor.
The linearity is determined by the digital-analog converter. If the linearity of the DAC is degraded, the precise operation of the VCM is difficult, and the accuracy of the AF function of the camera module cannot be ensured.